Fox was the true main antagonist in the 1981 anime film The Enchanted Journey.
He was presented as a relentless beast that roared like a dinosaur and struck terror into the hearts of all the Siberian chipmunks, even moreso than their other main enemy, Hawk.
Fox first appears when Glikko and Nono make it to the snowy mountains and get attacked by Hawk. Fox intervenes and battles Hawk. While the two predators are fighting, the chipmunks escape. After they're gone, Fox kills Hawk, and with blood-drenched lips turns and looks ominously in the direction Nono and Glikko went.
At the end of the film, when the pair are reunited with the other Siberian chipmunks in the forest, Pippo sees Fox coming, having followed Glikko and Nono. The chipmunks flee in terror from the beast, whilst Glikko, blaming himself for leading Fox to where all the chipmunks live, tries to fend him off. Nono attempts to help, but is vicious batted aside. So too does Pippo the pigeon, but Fox grievously wounds him. Both of them survive and Fox pursues Glikko to the edge of a cliff.
Jutting from the cliff there was a branch and Glikko scurried out onto it. Fox followed, threatening to snap the branch with his weight. Across the gulf was Glikko's only salvation; the other side of the ravine. The other chipmunks, looking on, called for their friend to jump. Glikko finally leaped - just as Fox did, too, snapping the branch.
Fox's claws raked across Glikko's back in midair, but only succeeded in tearing Glikko's bandana. Glikko made it safely across while the chipmunks' most dreaded enemy fell victim to gravity; Fox and the broken branch plummeted soundlessly down the gorge and out of sight.